I've read few question about grace period, but I didn't find approach that I was thinking of. If it's duplicate - sorry at the start.
I use SO frequently last days and I found that posting an answer to relatively simple questions is like a war: everybody post "an excerpt" as answer (which is laconic, but correct), then collect votes up (or even acceptation) while editing and reformatting own answer, taking profit from grace period. It's frustrating, because non-native-english users, especially those precisians like me, are sufferers of this approach, because it takes more time to read question and of course to write an answer.
While user X is writing a good answer, with formatting, code revision and improvements (sometimes not related to question, but welcome) other users post their (sometimes poor) answers and get points which could go to X. If answer was accepted, answer may not be edited even and stays on SO as a junk.
What I think, this shouldn't work this way. There should be a grace period for editing own answer after posting (let's say 5 minutes) because for answer editing proofreading should be done before posting, not after that. Then should be second grace period - this one which is now (editing without revision history and information below the post), or not - because user would write the answer more precisely when he would know that he can't edit for a while. Maybe size of a diff should matter - that user could edit typos and little fixes, but could not double the answer.